Nut shelling is the mechanical cracking of the hard shell to release the kernel, using centrifugal, shear or compression crackers calibrated by size fraction, with whole-kernel yield and shell contamination as the primary performance measures.
In trade practice
Crackers must be adjusted for each size fraction of in-shell nuts; using a single setting across mixed sizes increases both kernel breakage and uncracked nuts, reducing whole-kernel yield and grade value. Shell fragments remaining in the kernel stream are a critical quality defect and a potential physical hazard, requiring downstream sorting to meet buyer tolerances. Yield data from shelling runs are used by suppliers to cost kernel lots and by buyers to verify that declared kernel-to-shell ratios are realistic. Some EU buyers require a shell-fragment test result on the certificate of analysis.
In a specification
A kernel purchase specification typically states the maximum permitted shell-fragment content by weight and the minimum whole-kernel percentage, both verified at point of packing.